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Chemistry LibreTexts

Procedures: The Module

  1. How are the analytes separated by MEKC? Describe fundamental principles that govern the method.
  2. Define retention factor (or capacity factor) as it pertains to MEKC. Write the equation you would use to calculate the retention factor of tolmetin in pH 10, CAPs buffer 100 mM SDS. Describe what experiments are necessary to obtain each factor.
  3. Write a standard operating procedure for the separation of an unknown sample using MEKC. Assume this “unknown” contains three NSAIDS dissolved in background electrolyte (BGE). Be sure to include instructions for making BGE and implementing the technique.
  4. Determine the migration time for dimethylformamide and tolmetin for 3 consecutive free zone capillary electrophoresis runs. In addition, determine the migration time for dimethylformamide, tolmetin and n-decanophenone for 3 consecutive MEKC runs. Sample should be dissolved in background electrolyte (BGE). The sample for free zone capillary electrophoresis should contain 0.01% DMF and 300 micromolar tolmetin, while the sample for MEKC should contain 0.01% DMF, 300 micromolar tolmetin, and 300 micromolar n-decanophenone. This run buffer, or BGE, for the free zone capillary electrophoresis is 25 mM CAPs buffered to pH 10. The run buffer for the MEKC separations is 25 mM CAPs, 25 mM SDS buffered to pH 10. You must use a ~25 micron inner diameter fused silica capillary ~42 cm total length, ~32 cm to the window, 20 kV applied voltage. Be sure to flush the capillary adequately before each set (either free zone or MEKC). You may use the tables below to organize your data.
Free Zone DATA
Lw____, Lt____, _______ V
Trial Migration Time DMF Migration Time Tolmetin μ eof (CE) tolmetin μ app tolmetin μ eph
AVERAGE tolmetin μ eph  


Lw____, Lt____, _______V
Trial Migration Time DMF Migration Time Tolmetin Migration Time n-dec μ eof (MEKC) tolmetin k'


AVERAGE tolmetin k’